The CryptTalk account itself can only be used on a single device at a time. This is for security reasons, as the private key is stored on the phone and cannot be duplicated; however, each App Store subscription can have two accounts attached to it.
In order to have two CryptTalk accounts, please do the following:
- Make sure you use the same App Store account / Apple ID on your iPhone and iPad
- Purchase the subscription on one of your devices.
- Create a new account on the secondary device.
- On the secondary device perform a “restore purchases” operation, and you license will be granted.
Please note that if you perform a “restore purchase” on a third device, one of the previous devices will lose the license.